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Re: weak etags vs PATCH, was: Fwd: New Version Notification - draft-dusseault-http-patch-15.txt

From: Lisa Dusseault <lisa.dusseault@gmail.com>
Date: Mon, 19 Oct 2009 11:21:26 -0700
Message-ID: <ca722a9e0910191121ra11e924va9c0bda4fb0ab363@mail.gmail.com>
To: Julian Reschke <julian.reschke@gmx.de>
Cc: Mark Nottingham <mnot@mnot.net>, HTTP Working Group <ietf-http-wg@w3.org>
On Fri, Oct 16, 2009 at 4:33 AM, Julian Reschke <julian.reschke@gmx.de> wrote:

> Recommending the use of timestamps instead a potentially available weak etag
> simple does not make sense. After all, the server is minting the etags, and
> it also controls what it accepts in conditional PATCH requests. Let it
> decide what's right.
>

It looks to me like RFC2616 forbids this even if the server could
figure out what's right.

Section 14.26 says "The weak comparison function can only be used with
GET or HEAD requests."  So in a PATCH, we'd have to use strong
comparison.

Section 13.3.3 defines strong comparison:  "in order to be considered
equal, both validators MUST be identical in every way, and both MUST
NOT be weak."

Thus, a weak ETag could never successfully be used in a PATCH
operation, because weak comparison is forbidden and strong comparison
must fail.

We could include an explanation of how this is forbidden in the PATCH
draft, if you think that would help.

Lisa
Received on Monday, 19 October 2009 18:22:01 GMT

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